Which of the following best describes a Denial of Service (DoS) attack?

A Denial of Service (DoS) attack is best described by overwhelming a server with traffic to make it unavailable. This type of attack aims to render the targeted server, service, or network inaccessible to legitimate users. By flooding the server with excessive requests or data, the attacker exhausts the server's resources, which can lead to slowdowns or complete shutdowns, effectively denying service to genuine users.

This understanding distinguishes a DoS attack from other attack types. For instance, exploiting vulnerabilities in software refers to attacks that take advantage of flaws in applications to execute unauthorized actions, rather than solely hindering access. Accessing sensitive information illegally relates to data breaches or hacking incidents that focus on information theft rather than service disruption. Finally, installing malware for data theft emphasizes the use of malicious software to compromise systems for data exfiltration, which is a different goal from simply causing service unavailability. Thus, the key characteristic of a DoS attack is its focus on overwhelming systems to deny access rather than targeting information or exploiting vulnerabilities directly.